05-06-2019, 06:21 AM
I think Terry proposed the idea of a SAW filter in another thread but it's more elegant to do the job in digits.
For easy filtering the clock frequency in a digital modulator needs to be at least 4x the highest wanted output. Would need to look at DACs etc but I susepct the sweet spot for an IF modulator lies in the 20Mhz to 30MHz range, with a clock around 100MHz. I think Frank has been experimenting with direct modulation fo channel B1 (45MHz vision) and a clock around 180MHz. This is entirely feasible with modern DACs. Pushing up Band I could get difficult and DDS at Band III just looks too hard with a need for 700MHz+ clocks. It's feasible but not something you'd want to DIY.
For easy filtering the clock frequency in a digital modulator needs to be at least 4x the highest wanted output. Would need to look at DACs etc but I susepct the sweet spot for an IF modulator lies in the 20Mhz to 30MHz range, with a clock around 100MHz. I think Frank has been experimenting with direct modulation fo channel B1 (45MHz vision) and a clock around 180MHz. This is entirely feasible with modern DACs. Pushing up Band I could get difficult and DDS at Band III just looks too hard with a need for 700MHz+ clocks. It's feasible but not something you'd want to DIY.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
